JPH036638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a control device for an exposure lamp in a microfilm camera, etc., and in particular a lamp that controls the illuminance of an exposure lamp by preheating and lighting it during periods other than exposure. The present invention relates to an illuminance control device.

(Prior Art) FIG. 1 shows an example of a microfilm camera to which the present invention can be applied, in which an original for copying is placed on a transparent glass stage 1 via an original presser 2, manually or The exposure lamp 3 for this document is placed automatically.
The reflected light 4 is reflected by mirrors 5 and 6 arranged below.
It is designed to be input to the camera unit 10 via. A shutter 11 that can be opened and closed for transmitting or blocking light is disposed at the entrance of the camera unit 10, and when the shutter 11 is opened, the input light passes through a lens system 12 and forms an image. The original is recorded by exposing the film 13 to light.

For the above-mentioned microfilm camera, the second
The figure shows an example of a mechanism for automatically placing an original on the glass stage 1, and the original for copying is inserted into the entrance 20. When a document is inserted, the sensor 21 provided at the entrance 20 detects the insertion, and a drive motor (not shown) is driven to rotate the tension pulley 22 and the live pulley 23. be done. A flat belt 25 is wound between the tension pulley 22 and the live pulley 23 via a tension pulley 24 provided in the middle.
Following the movement of the flat belt 25, the inserted document passes between the tension roller 26 and reaches the top of the glass stage 1. When the original reaches the glass stage 1 in this way, the sensor 27 provided in the copying section optically detects the leading edge of the original, the drive motor is stopped, and the original is placed on the glass stage 1. , In this state, recording as described above is performed. After the recording is completed, the drive motor is driven again, and the recorded document is discharged from the outlet 30 through the path between the drive pulley 23 and the contact rollers 28 and 29, and the document is discharged from the stacker 3.
It seems to be stacked on top of 1.

Here, in the microfilm camera, the amount of light from the exposure lamp 3 changes due to fluctuations in the power supply, and there is a problem in that the device may malfunction due to fluctuations in the amount of light. That is, when the power supply voltage increases, the light intensity of the exposure lamp 3, which is preheated and lit except during main exposure, increases significantly even when the preheating lamp is lit, so that the document cannot be detected based on the light intensity of the exposure lamp 3. There was a drawback that the sensor 27 malfunctioned, making it impossible to record accurately on the film 13.

(Problems to be Solved by the Invention) For these reasons, conventionally, an illuminance control device as shown in FIG. 3 has been used to control the light amount of the exposure lamp 3 of the microfilm camera. That is, the exposure lamp 3 is connected to an AC power source (for example, a commercial power source) 42 via a bidirectional thyristor 41, and a transformer 43 is connected to both ends of the exposure lamp 3 in order to detect the voltage applied to the exposure lamp 3. The secondary voltage of the transformer 43 is converted into direct current by the rectifier circuit 44. Then, the DC voltage obtained by the rectifier circuit 44 is input to a comparison amplifier 45 and compared with a constant reference voltage V _r . Based on this comparison result, the lighting control circuit 4
The illuminance of the exposure lamp 3 is controlled to be constant by controlling the firing phase angle θ of the bidirectional thyristor 41 via the thyristor 6.

However, in such a conventional control device, the firing phase angle θ of the bidirectional thyristor 41 is controlled by converting the voltage fluctuation of the AC power supply 42 into a DC voltage and comparing it with a constant reference voltage V _r . Therefore, as shown in Figure 4 (90V),
(100V), (110V) when the voltage of the AC power supply 42 fluctuates, the reference voltage V _{r is} always constant.
As shown in the figure, the firing phase angle θ of the bidirectional thyristor 41 is θ ₁
>θ ₂ >θ ₃ . In this way, since the constant reference voltage V _r and the voltage of the AC power supply 42 are always compared, the firing phase angle θ of the bidirectional thyristor 41 decreases as the voltage of the AC power supply 42 increases. However, the ignition area is not constant. In other words, the energy for lighting the lamp is not constant. For this reason, the relationship between the power supply voltage V and the illuminance (lux) of the exposure lamp 3 shown in FIG. 5 is not constant, and the relationship has a slope characteristic as shown in characteristic A or B in the same figure. There is. In this way, even in the control device shown in FIG. 3, the illuminance of the exposure lamp 3 changes due to fluctuations in the power supply voltage V, so that the sensor 27 may malfunction as described above.

Furthermore, FIG. 6 shows another example of an illuminance control device for the exposure lamp 3 using a bidirectional thyristor 41, in which a time constant control circuit 47 consisting of a resistor R ₀ and a capacitor C ₀ controls the trigger diode 4.
8 controls the firing phase angle of the bidirectional thyristor 41. However, in the case of this illuminance control device, the voltage applied to the time constant control circuit 47 also fluctuates due to fluctuations in the AC power supply 42, so as shown by the broken line characteristic C in FIG.
The voltage-illuminance characteristic changes more greatly as the voltage drops, and when the voltage of the AC power source 42 drops to around 90V, there is a drawback that the exposure lamp 3 is turned off during exposure.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a lamp illuminance control device that does not have the above-mentioned drawbacks. That is, it is an object of the present invention to provide a compact lamp illuminance control device that can always maintain a constant lamp illuminance even when the power supply voltage fluctuates.

(Means for Solving the Problems) This invention relates to an illuminance control device for an exposure lamp in a microfilm camera, a copying machine, etc., and the above object of the invention is to full-wave rectify the AC power applied to the lamp. a full-wave rectifier smoothing circuit for smoothing; a pulsating wave circuit for converting the AC power into a pulsating wave; and comparing the pulsating wave with a partial pressure value of the full-wave rectifying and smoothing output to output a lighting control signal. a comparison circuit, a zero-crossing signal generating circuit for forming a zero-crossing signal of the AC power source from the pulsating current wave, and inputting the lighting control signal, and for lighting the lamp from the zero-crossing signal in synchronization with the zero-crossing signal. This is achieved by providing a lamp lighting signal forming circuit for forming a lamp lighting signal, and a lamp driving circuit for driving the lamp to be lit based on the lamp lighting signal.

(Function) In this invention, a divided voltage is taken from the AC power supply used for lighting the lamp, and the firing phase angle of the bidirectional thyristor can be arbitrarily adjusted. The illumination intensity is controlled to be constant as shown by characteristic D in FIG. Therefore, it is possible to reliably prevent the microfilm camera from malfunctioning due to changes in the illuminance of the exposure lamp due to fluctuations in the power supply.

(Embodiment) In this invention, as shown in FIG. 7, a full-wave rectifying and smoothing circuit 1 that full-wave rectifies and smoothes an AC power supply 101 applied to an exposure lamp 3 via a transformer 102.
10, a pulsating current wave circuit 120 that converts the AC power source 101 into a pulsating current wave MW, and a pulsating current wave circuit 120 that compares the pulsating current wave MW with the partial pressure value DV of the full-wave rectified smoothed output V _DD to generate a lighting control signal LC.
a comparison circuit 130 that outputs
a zero-crossing signal generation circuit 140 that forms a zero-crossing signal ZS of the AC power supply 101 using the pulsating wave MW from the lamp; and a lamp that forms a lamp lighting signal LL for lighting the lamp 3 from the lighting control signal LC and the zero-crossing signal ZS. Lighting signal forming circuit 15
0 and a lamp drive circuit 160 that drives the lamp 3 to light it via a bidirectional thyristor 161 in response to a lamp lighting signal LL inputted via an OR circuit 103.

Further, the full-wave rectifying and smoothing circuit 110 includes a transformer 1
A full-wave rectifier 111 for rectifying the secondary voltage of 02 with a diode bridge, a capacitor _C1 for smoothing this output, a stabilizing circuit 112 for stabilizing the rectified output, and this stabilizing circuit. 11
The full-wave rectifying and smoothing output V _DD of this full-wave rectifying and smoothing circuit 110 serves as a stabilized DC power supply for a comparator circuit 130 , a zero-crossing signal generating circuit 140 , and a lamp _. The signals are supplied to the drive circuit 160, respectively. Furthermore, the pulsating wave circuit 120 is composed of two parallel-connected diodes 121 and 122 for half-wave rectification of the secondary voltage of the transformer 102, and the comparison circuit 130 is composed of a transistor that performs level comparison and judgment. 131, and a Schmitt circuit 132 for waveform shaping the collector output of this transistor 131. A voltage obtained by dividing the pulsating current wave MW by a variable resistor _R1 is applied to the base of the transistor 131, and the collector output is applied to the base of the transistor 131. A stabilized DC power supply V _DD is applied to through a resistor R ₂ . The unstabilized rectified output of the rectifier 111 is connected to the emitter of the transistor 131 by a resistor R ₃
It is given as a partial pressure value DV divided by R4 and _R4 .

On the other hand, the zero cross signal generation circuit 140 generates the pulsating flow wave MW from the pulsating flow wave circuit 120 through the resistors R ₇ and R _{8 .}
The emitter of the transistor 141 is grounded, and the stabilized DC power supply _VDD is applied to the collector of the transistor 141 via a low resistor _R9 . , the collector output of the transistor 141 is waveform-shaped by the Schmitts circuit 142 and output as a zero-cross signal ZS to the lamp lighting signal forming circuit 150.
The signal is input to the reset terminal R of the R-S flip-flop 155. The lamp lighting signal forming circuit 150 also has a JK flip-flop 154 that inputs the lamp lighting signal LC from the comparator circuit 130, and its Q output is input to the set terminal S of the flip-flop 155. is input to the AND circuit 153 and the inverter 152. and,
The output of the inverter 152 is inputted to the R terminal of the J-K flip-flop 154 via the inverter 151, and is also inputted to the AND circuit 153 via resistors _R5 and _R6 , and the connection point between the resistors _R5 and _R6 is the capacitor C. ₃ is grounded through. The lamp lighting signal LL output from the AND circuit 153 is
The voltage is applied to the base of the transistor 162 of the lamp drive circuit 160 through the OR circuit 103, and the collector of the transistor 162 is connected to the stabilized DC power supply V _DD through the primary winding of a small pulse transformer 163. The secondary output of the pulse transformer 163 is connected to the bidirectional thyristor 16.
1 at a predetermined angle.

Note that the OR circuit 103 has a lamp continuous lighting signal.
FL is input and this lamp continuous lighting signal
When FL is input, lamp 3 lights up continuously.

In such a configuration, its operation is shown in Fig. 8A.
This will be explained with reference to timing charts shown in ~E.

The AC waveform of the AC power supply 101 is
is input to the diodes 121 and 122 of the pulsating current wave circuit 120 through the pulsating current wave circuit 120, and is converted into the pulsating current wave MW as shown in FIG. Transistor 141 of circuit 140
are applied to the base of each. The secondary voltage of the transformer 102 is full-wave rectified by the rectifier 11, smoothed by the capacitor _C1 , and then passed through the comparison circuit 130.
and in the comparator circuit 130, resistors R ₃ and R ₄
The divided voltage DV is applied to the emitter of the transistor 131. As a result, the transistor 131 has a difference in emitter-base potential (approximately
0.7V). In this case, if the voltage of the AC power supply 101 fluctuates as shown in FIG. It changes. Therefore, if the magnitude of the rectified output (divided voltage value DV) in case of A in Fig. 8 is the voltage DV ₁ , then as the pulsating flow wave MW increases as shown in the figure, the rectified output also increases accordingly. Therefore, transistor 131
The divided voltage applied to the emitter of is also a voltage DV ₂ which is larger than the voltage DV ₁ .

Thus, transistor 131 connects resistor R ₃ and
Based on the divided voltage DV divided by _R4 , the input pulsating current wave MW is binarized as shown in FIG. Lighting signal forming circuit 150
input to the flip-flop 154 of. In this case, even if the voltage increases as shown in Figure 8A, the reference divided voltage value DV also increases accordingly, so the pulse width of the lighting control signal LC changes. Never. lighting control signal
When LC is input to the C terminal of the flip-flop 154, the Q output of the flip-flop outputs an impulse at the rising edge of the lighting control signal LC, as shown in FIG.
Set. And flip-flop 155
The Q output of is input to the AND circuit 153, and is also input to the R terminal of the flip-flop 154 via inverters 152 and 151, and is sent to the AND circuit 153 with a delay of a time constant determined by the resistor _R5 and the capacitor _C3 . The AND circuit 153 outputs the lamp lighting signal LL based on the logical product.
Here, the zero cross signal generating circuit 140 inputs the pulsating current wave MW, and due to the Schmitt action of the transistor 141, the signal shown in FIG.
A zero-crossing signal ZS as shown in FIG. 1 is generated and inputted to the reset terminal R of the flip-flop 155, so that the Q output of the flip-flop 155 is reset to "L" at the time of this input. After the Q output of the flip-flop 155 becomes "H", "H" is input to the AND circuit 153 with a time constant determined by the resistor _R5 and the capacitor _C3 , so the output of the AND circuit 153 is , that is, the lamp lighting signal LL is output from the flip-flop 15.
5 is set and until it is reset, and only during the time constant _R5.C3 , this lamp lighting signal LL is output to _the OR circuit 103 and the resistor _R10.
The signal is input to the base of the transistor 162 via the . As a result, the bidirectional thyristor 161 is turned on via the pulse transformer 163 at phase angles θ ₁ and θ ₂ as shown in FIG. 8E, and the lamp 3 is turned on during this time.

As described above, the reference level for comparison is set by the rectifier 11 in accordance with the change in the magnitude of the pulsating current wave MW caused by the change in the voltage of the AC power supply 101.
The output of 1 is divided by resistors R ₃ and R ₄ to obtain a voltage DV. Therefore, when the voltage of AC power supply 101 increases, divided voltage DV also increases, and when AC power supply 101 drops, divided voltage DV decreases accordingly. The rate of change of the divided voltage DV, which is the reference voltage, can be adjusted arbitrarily by appropriately changing the voltage dividing ratio of the resistors R ₃ and R ₄ . The bidirectional thyristor 16 as shown in FIG.
The firing area can be made constant by arbitrarily adjusting the firing phase angle θ of 1. As a result, the relationship between the power supply voltage V and the illuminance of the lamp 3 shown in FIG. 5 can always be kept constant (characteristic D).

In addition, in the above-mentioned embodiment, an example was given in which the comparison circuit was composed of a transistor and a Schmitt circuit.
It is also possible to use an IC element comparator, and other circuits can also be integrated into ICs. Also,
By appropriately adjusting the voltage dividing ratio of the resistor _R1 connected to the base side of the transistor 131 in the comparator circuit 130, and the voltage dividing ratio of the resistors _R3 and _R4 , which are the reference voltage input to the emitter, respectively. The pulse width change of the lighting control signal LC, that is, the characteristic curve shown in FIG. 5, can be changed arbitrarily.

(Effects of the Invention) As described above, according to the lamp illuminance control device of the present invention, a constant lamp illuminance can always be maintained even when the power supply voltage fluctuates, and a compact configuration can be achieved. Therefore, the microfilm camera will not malfunction due to changes in the illuminance of the exposure lamp due to fluctuations in the power supply.

[Brief explanation of drawings]

1 and 2 are schematic structural diagrams of a microfilm camera to which the present invention can be applied, FIG. 3 is a block configuration diagram showing an example of a conventional lamp illuminance control device, and FIG. 4 shows its characteristics. Figure 5 is a diagram for explaining how the power supply voltage changes and lamp illuminance changes. Figure 6 is a wiring diagram showing another example of a conventional lamp illuminance control device. FIG. 7 is a circuit configuration diagram showing one embodiment of the present invention, and FIGS. 8A to 8E are timing charts showing examples of its operation. 1...Glass stage, 2...Document holder, 3...
...Exposure lamp, 5, 6...Mirror, 10...Camera unit, 11...Shutter, 12...Lens system, 13...Film, 21, 27...Sensor, 41,100...Bidirectional thyristor , 4
2,101... AC power supply, 43,102... Transformer, 44... Rectifier circuit, 45... Comparative amplifier,
46...Lighting control circuit, 110...Full wave rectification smoothing circuit, 120...Ripple wave circuit, 130...Comparison circuit, 14...Zero cross signal generation circuit, 150...
... Lamp lighting signal forming circuit, 160 ... Lamp drive circuit.

Claims (1)

[Claims] 1. A full-wave rectifying and smoothing circuit that full-wave rectifies and smoothes the AC power applied to the lamp; a pulsating wave circuit that converts the AC power into pulsating waves; and a pulsating wave circuit that converts the pulsating waves into the full-wave rectifying and smoothing output. a comparison circuit that outputs a lighting control signal by comparing it with a partial voltage value; a zero-crossing signal generation circuit that forms a zero-crossing signal of the AC power source from the pulsating wave; A lamp lighting signal forming circuit that inputs an input signal to form a lamp lighting signal for lighting the lamp in synchronization with the zero cross signal, and a lamp driving circuit that drives the lamp to turn on based on the lamp lighting signal. A lamp illuminance control device characterized by: